Water-quality data about beaches on Long Island Sound has been publicly available for a while, but understanding it can be tricky. Now, a new online tool could help make that process easier.

When it comes to bacteria on the shoreline, the question isn’t if it’s there, it’s how much.

“Every week, in the summer, the Departments of Health around the regions go out and collect a sample at each of our beaches and all of that data has been collected by [the] EPA,” said Tracy Brown, with Save the Sound, an environmental organization.

Brown said that usually, a little bacteria isn’t enough to close a beach, but higher concentrations can. So, to get a handle on which beaches weren’t meeting water quality standards, Save the Sound combed through ten years of EPA data assigning a letter grade of A through F to each beach. Then they took that info and mapped it, creating the Sound Health Explorer.

“We saw beaches along the Connecticut shoreline in the New Haven to Stamford region having grades that were decreasing, so that’s a source of concern,” said Brown.

The tool also breaks out whether or not beaches that failed water-quality testing following a rainstorm.

“It’s not uncommon for beaches to have too much bacteria and fecal contamination in the water after rain. Because rain will flush a lot of waste off the beaches and streams and creeks that have pollution in them will flow at a higher rate into a nearby beach,” Brown said. “But you really shouldn’t see failures in dry weather. Dry weather means that there’s a source — like a failing sewer system or septic systems that are failing in wet weather and dry, so if that’s going on — you’re getting a failing grade in this tool.”

According to Sound Health Explorer, Green Harbor Beach in New London was the only one that got an F. Sea Bluff Beach in West Haven got D minus, and Branford Point Beach got a D.

In the future, Brown said the hope is to also add water-quality data about non-beach locations like streams and harbors.